Mechanisms

16 Articles

One of the challenges with humanoid robots, besides keeping them upright, is finding compact combinations of actuators and joint mechanisms that allow for good range of smooth motion while still having good strength. To achieve that researchers from the IRIM Lab at Korea University of Technology and Education developed the LIMS2-AMBIDEX robotic humanoid upper body that uses a combination of brushless motors, pulleys and some very interesting joint mechanisms. (Video, embedded below.)

The wrist mechanism. Anyone willing to tackle a 3D printed version?

From shoulder to fingers, each arm has seven degrees of freedom which allows the robot to achieve some spectacularly smooth and realistic upper body motion. Except for the wrist rotation actuator, all the actuators are housed in the shoulders, and motion is transferred to the required joint through an array of cables and pulleys. This keeps the arm light and its inertia low, allowing the arms to move rapidly without breaking anything or toppling the entire robot.

The wrist and elbow mechanisms are especially interesting. The wrist emulates rolling contact between two spheres with only revolute joints. It also allows a drive shaft to pass down the centre of the mechanism and transfer rotating motion from one end to the other. The elbow is a rolling double jointed affair that allows true 180 degrees of rotation.

There was a time, not so very long ago, when simply getting a 3D printer to squirt out an object that was roughly the intended shape and size of what the user saw on their computer screen was an accomplishment. But like every other technology, the state of the art has moved forward. Today the printers are better, and the software to drive them is more capable and intuitive. It was this evolution of desktop 3D printing that inspired the recently concluded 3D Printed Gears, Pulleys, and Cams contest. We wanted to see what hackers and makers can pull off with today’s 3D printing tools, and the community rose to the challenge.

Let’s take a look at the top ten spinning, walking, flapping, and cranking 3D printed designs that shook us up:

One of the killer apps of 3D printers is the ability to make custom gears, transmissions, and mechanisms. But there’s a learning curve. If you haven’t 3D printed your own gearbox or automaton, here’s a great reason to take the plunge. This morning Hackaday launched the 3D Printed Gears, Pulleys, and Cams contest, a challenge to make stuff move using 3D-printed mechanisms.

Adding movement to a project brings it to life. Often times we see projects where moving parts are connected directly to a servo or other motor, but you can do a lot more interesting things by adding some mechanical advantage between the source of the work, and the moving parts. We don’t care if it’s motorized or hand cranked, water powered or driven by the wind, we just want to see what neat things you can accomplish by 3D printing some gears, pulleys, or cams!

No mechanism is too small — if you have never printed gears before and manage to get just two meshing with each other, we want to see it! (And of course no gear is literally too small either — who can print the smallest gearbox as their entry?) Automatons, toys, drive trains, string plotters, useless machines, clockworks, and baubles are all fair game. We want to be inspired by the story of how you design your entry, and what it took to get from filament to functional prototype.

Translating rotary motion to linear motion is a basic part of mechatronic design. Take a look at the nearest 3D-printer or CNC router — at least the Cartesian variety — and you’ll see some mechanism that converts the rotation of the the motor shafts into the smooth linear motion needed for each axis.

Hobby-grade machines are as likely as not to use pulleys and timing belts to achieve this translation, and that generally meets the needs of the machine. But in some machines, the stretchiness of a belt won’t cut it, and the designer may turn to some variety of screw drive to do the job.

In our “Mechanisms” series, we’ve featured the fascinating bits and pieces that go into making our mechanical world work. From simple machines such as screws and levers, from springs to couplings, and even more complex mechanisms like zippers and solenoids, we’ve covered the gamut. But we haven’t talked about one of the very earliest mechanisms, captured from nature by our clever ancestors to do useful work like grinding grain and shaping materials into tools: grit, sand, abrasives.

Since humans first starting playing with electricity, we’ve proven ourselves pretty clever at finding ways to harness that power and turn it into motion. Electric motors of every type move the world, but they are far from the only way to put electricity into motion. When you want continuous rotation, a motor is the way to go. But for simpler on and off applications, where fine control of position is not critical, a solenoid is more like what you need. These electromagnetic devices are found everywhere and they’re next in our series on useful mechanisms.

Levers are literally all around us. You body uses them to move, pick up a pen to sign your name and you’ll use mechanical advantage to make that ballpoint roll, and that can of soda doesn’t open without a cleverly designed lever.

I got onto this topic quite by accident. I was making an ornithopter and it was having trouble lifting its wings. For the uninitiated, ornithopters are machines which fly by flapping their wings. The problem was that the lever arm was too short. To be honest, as I worked I wasn’t even thinking in terms of levers, and only realized that there was one after I’d fine-tuned its length by trial and error. After that, the presence of a lever was embarrassingly obvious.

I can probably be excused for not seeing a lever right away because it wasn’t the type we most often experience. There are different classes of levers and it’s safe to say that most people aren’t even aware of this. Let’s take a closer look at these super useful, and sometimes hidden mechanisms known as levers.